Fuel systems used in state-of-the-art internal combustion engines tend to be relatively complex. The associated engines can be direct-injected where a fuel injector is positioned at least partially within an engine cylinder, port injected where fuel is delivered into a port in communication with an engine cylinder, or structured according to yet another strategy where fuel is delivered at a location upstream of an engine cylinder into an intake runner or an intake manifold, or for some gaseous fuel engines, delivered upstream a compressor of a turbocharger.
In the case of compression ignition diesel engines it is typical for liquid fuel injection pressures to be as high as several hundred megaPascals (MPa). Injections can occur multiple times per second, necessitating rapid travel of moving parts within the fuel injector in response to electromagnetic actuation forces and/or rapid pressure changes, and resulting in relatively intense, repetitive impacts, and in some instances a tendency toward liquid cavitation. The timing and manner of injection of fuel is typically relatively tightly controlled, with opening and closing of valves desirably quite rapid to produce so-called “square” injection rate shapes. Pressurization of the fuel to be injected can take place within the fuel injector itself, such as by way of a hydraulically actuated or cam-actuated piston, or in a common rail or related system where a common reservoir of highly pressurized fuel is maintained for multiple fuel injectors.
Performance analysis and fault detection in fuel systems can be challenging, given a relatively great number of moving parts, harsh conditions, and still other factors. One example fuel injector for an internal combustion engine is known from U.S. Pat. No. 8,690,075.